1. Field of the Invention
The present invention relates to a gas turbine used as a main engine and an auxiliary engine (APU) for aircraft, vehicles, industrial purposes and so forth, and a thrust gas turbine engine (turbojet, turbofan) used primarily as a main engine for aircraft.
Further, the present invention relates to an operating method of the above-mentioned gas turbine.
2. Description of the Related Art
FIG. 5 is a longitudinal sectional view showing an example of a conventional gas turbine engine. Air suctioned through an air inlet port 1 is compressed by an axial-flow compressor 2 and a centrifugal compressor 3 and led to a combustor 4, where the compressed air is used for combustion of fuel. A high-pressure turbine 5 and an output turbine 6 are driven to rotate by combustion gas produced by combustion. The axial-flow compressor 2 and the centrifugal compressor 3 mentioned above are driven by the rotation of the high-pressure turbine 5. The torque of the output turbine 6 is taken out through an output shaft 7. A numeral 8 denotes a full authority digital electronic control (FADEC) device. Increase and decrease of the output is performed by regulating the supply quantity of fuel so as to vary the speed of engine rotation. In the above-mentioned axial-flow compressor 2, a variable inlet guide vane 9 is provided on an inlet side and a variable stationary vane 10 is provided on an outlet side, respectively, in order to prevent surging, and angles thereof are controlled by means of the FADEC device 8.
Next, FIG. 6 is a longitudinal sectional view showing another example of a conventional gas turbine engine. In this example, a variable turbine nozzle 11 is provided at the inlet of the output turbine 6, and output responsiveness is increased by rapidly moving the variable turbine nozzle 11 by means of the FADEC device 8. Since only the centrifugal compressor 3 is provided as the compressor, and no axial-flow compressor is provided, neither the variable inlet guide vane nor the variable stationary vane is provided.
There have been such problems to be solved in above-mentioned conventional gas turbine engine as follows.
In a gas turbine engine illustrated in FIG. 5, it is required to vary the engine rotation for regulating the output. Accordingly, the output response time is affected by the rotational moment of inertia of a rotor, and there has been a limit for reducing the speed of rotation of the engine. Namely, time is required in order to accelerate and decelerate a rotary body having large inertial mass. Since the variable inlet guide vane 9 and the variable stationary vane 10 are provided to avoid surging, the variable range is narrow and large output variation is not obtainable even if these vanes are moved.
Further, there is such a problem that surging occurs when the variable inlet guide vane 9 and the variable stationary vane 10 are altered to such an extent that output can be varied.
In a gas turbine engine illustrated in FIG. 6, output responsiveness is increased by moving the variable turbine nozzle 11 rapidly and fuel consumption at partial load is also improved further, but there have been problems in reliability, performance and weight because the variable mechanism has to be installed at a high temperature portion. For example, since the variable mechanism is exposed to high temperature, it is required to keep a large clearance between the vane and the wall surface taking thermal expansion into consideration. The loss caused by leakage through the clearance becomes large thus deteriorating the performance.
Further, in a conventional thrust gas turbine engine, the engine rotation is varied by regulating the supply quantity of fuel to alter the output thereof.
When the engine rotation is varied in order to vary the output in a thrust gas turbine engine having no such variable mechanism, there has been a drawback that a certain period of time is required for acceleration and deceleration and high responsiveness cannot be achieved because the rotary body has a large inertial mass.
Further, in some thrust gas turbine engines, a variable nozzle is provided at an inlet of the turbine and the quantity of combustion gas which flows into the turbine is regulated by opening and closing the variable nozzle to alter the engine output.
In a thrust gas turbine engine including a turbine with a variable nozzle, the above-described problems are solved and fuel consumption with partial load is also improved. However, it is required to keep a large clearance between the vane and the wall surface taking thermal expansion into consideration because a variable mechanism has to be installed at a high temperature portion of the engine similarly to the engine illustrated in FIG. 6, thus causing problems in performance, reliability and weight such that leakage loss becomes large and performance deteriorates.